Unit-1 Operating System PDF

Unit -1 1) What is the operating system? Explain Function and Objectives? 2) Explain types of Operating system? 3) Explain generation of operating system? 4) What do you understand by System Protection in Operating system? 5) What is the booting? Explain Types of Booting? 6) Explain str...

Unit -1 1) What is the operating system? Explain Function and Objectives? 2) Explain types of Operating system? 3) Explain generation of operating system? 4) What do you understand by System Protection in Operating system? 5) What is the booting? Explain Types of Booting? 6) Explain structure of operating system? 7) What is the computer? Explain Types of Computer?  Q1. What is the operating system? Explain Function and Objectives? Operating system Operating System lies in the category of system software. It basically manages all the resources of the computer. An operating system acts as an interface between the software and different parts of the computer or the computer hardware. The operating system is designed in such a way that it can manage the overall resources and operations of the computer. Operating System is a fully integrated set of specialized programs that handle all the operations of the computer. It controls and monitors the execution of all other programs that reside in the computer, which also includes application programs and other system software of the computer. Examples of Operating Systems are Windows, Linux, Mac OS, etc. An Operating System (OS) is a collection of software that manages computer hardware resources and provides common services for computer programs. The operating system is the most important type of system software in a computer system. Functions of the Operating System Resource Management: The operating system manages and allocates memory, CPU time, and other hardware resources among the various programs and processes running on the computer. Process Management: The operating system is responsible for starting, stopping, and managing processes and programs. It also controls the scheduling of processes and allocates resources to them. Memory Management: The operating system manages the computer’s primary memory and provides mechanisms for optimizing memory usage. Security: The operating system provides a secure environment for the user, applications, and data by implementing security policies and mechanisms such as access controls and encryption. Job Accounting: It keeps track of time and resources used by various jobs or users. File Management: The operating system is responsible for organizing and managing the file system, including the creation, deletion, and manipulation of files and directories. Device Management: The operating system manages input/output devices such as printers, keyboards, mice, and displays. It provides the necessary drivers and interfaces to enable communication between the devices and the computer. Networking: The operating system provides networking capabilities such as establishing and managing network connections, handling network protocols, and sharing resources such as printers and files over a network. User Interface: The operating system provides a user interface that enables users to interact with the computer system. This can be a Graphical User Interface (GUI), a Command-Line Interface (CLI), or a combination of both. Backup and Recovery: The operating system provides mechanisms for backing up data and recovering it in case of system failures, errors, or disasters. Virtualization: The operating system provides virtualization capabilities that allow multiple operating systems or applications to run on a single physical machine. This can enable efficient use of resources and flexibility in managing workloads. Performance Monitoring: The operating system provides tools for monitoring and optimizing system performance, including identifying bottlenecks, optimizing resource usage, and analyzing system logs and metrics.  Time-Sharing: The operating system enables multiple users to share a computer system and its resources simultaneously by providing time-sharing mechanisms that allocate resources fairly and efficiently. System Calls: The operating system provides a set of system calls that enable applications to interact with the operating system and access its resources. System calls provide a standardized interface between applications and the operating system, enabling portability and compatibility across different hardware and software platforms. Error-detecting Aids: These contain methods that include the production of dumps, traces, error messages, and other debugging and error-detecting methods. Objectives of Operating Systems Let us now see some of the objectives of the operating system, which are mentioned below. Convenient to use: One of the objectives is to make the computer system more convenient to use in an efficient manner. User Friendly: To make the computer system more interactive with a more convenient interface for the users. Easy Access: To provide easy access to users for using resources by acting as an intermediary between the hardware and its users. Management of Resources: For managing the resources of a computer in a better and faster way. Controls and Monitoring: By keeping track of who is using which resource, granting resource requests, and mediating conflicting requests from different programs and users. Fair Sharing of Resources: Providing efficient and fair sharing of resources between the users and programs. Q2.Explain types of Operating system? Types of Operating Systems Batch Operating System: A Batch Operating System is a type of operating system that does not interact with the computer directly. There is an operator who takes similar jobs having the same requirements and groups them into batches. Time-sharing Operating System: Time-sharing Operating System is a type of operating system that allows many users to share computer resources (maximum utilization of the resources). Distributed Operating System: Distributed Operating System is a type of operating system that manages a group of different computers and makes appear to be a single computer. These operating systems are designed to operate on a network of computers. They allow multiple users to access shared resources and communicate with each other over the network. Examples include Microsoft Windows Server and various distributions of Linux designed for servers. Network Operating System: Network Operating System is a type of operating system that runs on a server and provides the capability to manage data, users, groups, security, applications, and other networking functions. Real-time Operating System: Real-time Operating System is a type of operating system that serves a real-time system and the time interval required to process and respond to inputs is very small. These operating systems are designed to respond to events in real time. They are used in applications that require quick and deterministic responses, such as embedded systems, industrial control systems, and robotics. Multiprocessing Operating System: Multiprocessor Operating Systems are used in operating systems to boost the performance of multiple CPUs within a single computer system. Multiple CPUs are linked together so that a job can be divided and executed more quickly.  Single-User Operating Systems: Single-User Operating Systems are designed to support a single user at a time. Examples include Microsoft Windows for personal computers and Apple macOS. Multi-User Operating Systems: Multi-User Operating Systems are designed to support multiple users simultaneously. Examples include Linux and Unix. Embedded Operating Systems: Embedded Operating Systems are designed to run on devices with limited resources, such as smartphones, wearable devices, and household appliances. Examples include Google’s Android and Apple’s iOS Q3.Explain generation of operating system? Operating System Generations Operating Systems have evolved over the years. So, their evolution through the years can be mapped using generations of operating systems. There are four generations of operating systems. These can be described as follows − The First Generation ( 1945 - 1955 ): Vacuum Tubes and Plugboards Digital computers were not constructed until the second world war. Calculating engines with mechanical relays were built at that time. However, the mechanical relays were very slow and were later replaced with vacuum tubes. These machines were enormous but were still very slow. These early computers were designed, built and maintained by a single group of people. Programming languages were unknown and there were no operating systems so all the programming was done in machine language. All the problems were simple numerical calculations. By the 1950’s punch cards were introduced and this improved the computer system. Instead of using plugboards, programs were written on cards and read into the system. The Second Generation ( 1955 - 1965 ): Transistors and Batch Systems Transistors led to the development of the computer systems that could be manufactured and sold to paying customers. These machines were known as mainframes and were locked in air-conditioned computer rooms with staff to operate them. The Batch System was introduced to reduce the wasted time in the computer. A tray full of jobs was collected in the input room and read into the magnetic tape. After that, the tape was rewound and mounted on a tape drive. Then the batch operating system was loaded in which read the first job from the tape and ran it. The output was written on the second tape. After the whole batch was done, the input and output tapes were removed and the output tape was printed. The Third Generation ( 1965 - 1980 ): Integrated Circuits and Multiprogramming Until the 1960’s, there were two types of computer systems i.e., the scientific and the commercial computers. These were combined by IBM in the System/360. This used integrated circuits and provided a major price and performance advantage over the second generation systems. The third generation operating systems also introduced multiprogramming. This meant that the processor was not idle while a job was completing its I/O operation. Another job was scheduled on the processor so that its time would not be wasted. The Fourth Generation ( 1980 - Present ): Personal Computers Personal Computers were easy to create with the development of large-scale integrated circuits. These were chips containing thousands of transistors on a square centimeter of silicon. Because of these, microcomputers were much cheaper than minicomputers and that made it possible for a single individual to own one of them. The advent of personal computers also led to the growth of networks. This created network operating systems and distributed operating systems. The users were aware of a network while using a network operating system and could log in to remote machines and copy files from one machine to another. Q4.What do you understand by System Protection in Operating system? System Protection in Operating System System protection in an operating system refers to the mechanisms implemented by the operating system to ensure the security and integrity of the system. System protection involves various techniques to prevent unauthorized access, misuse, or modification of the operating system and its resources. There are several ways in which an operating system can provide system protection: User authentication: The operating system requires users to authenticate themselves before accessing the system. Usernames and passwords are commonly used for this purpose. Access control: The operating system uses access control lists (ACLs) to determine which users or processes have permission to access specific resources or perform specific actions. Encryption: The operating system can use encryption to protect sensitive data and prevent unauthorized access. Firewall: A firewall is a software program that monitors and controls incoming and outgoing network traffic based on predefined security rules. Antivirus software: Antivirus software is used to protect the system from viruses, malware, and other malicious software. System updates and patches: The operating system must be kept up-to-date with the latest security patches and updates to prevent known vulnerabilities from being exploited. By implementing these protection mechanisms, the operating system can prevent unauthorized access to the system, protect sensitive data, and ensure the overall security and integrity of the system. What is Protection? Protection refers to a mechanism which controls the access of programs, processes, or users to the resources defined by a computer system. We can take protection as a helper to multi programming operating system, so that many users might safely share a common logical name space such as directory or files. Need for Protection: To prevent the access of unauthorized users To ensure that each active programs or processes in the system uses resources only as the stated policy To improve reliability by detecting latent errors Role of Protection: The role of protection is to provide a mechanism that implement policies which defines the uses of resources in the computer system. Some policies are defined at the time of design of the system, some are designed by management of the system and some are defined by the users of the system to protect their own files and programs. Every application has different policies for use of the resources and they may change over time so protection of the system is not only concern of the designer of the operating system. Application programmer should also design the protection mechanism to protect their system against misuse. Policy is different from mechanism. Mechanisms determine how something will be done and policies determine what will be done. Policies are changed over time and place to place. Separation of mechanism and policy is important for the flexibility of the system. Advantages of system protection in an operating system: 1. Ensures the security and integrity of the system 2. Prevents unauthorized access, misuse, or modification of the operating system and its resources 3. Protects sensitive data 4. Provides a secure environment for users and applications 5. Prevents malware and other security threats from infecting the system 6. Allows for safe sharing of resources and data among users and applications 7. Helps maintain compliance with security regulations and standards Disadvantages of system protection in an operating system: 1. Can be complex and difficult to implement and manage 2. May slow down system performance due to increased security measures 3. Can cause compatibility issues with some applications or hardware 4. Can create a false sense of security if users are not properly educated on safe computing practices 5. Can create additional costs for implementing and maintaining security measures. Q5. What is the booting? Explain Types of Booting? Booting in Operating System Booting is the process of starting a computer. It can be initiated by hardware such as a button press or by a software command. After it is switched on, a CPU has no software in its main memory, so some processes must load software into memory before execution. This may be done by hardware or firmware in the CPU or by a separate processor in the computer system. Restarting a computer also is called rebooting, which can be "hard", e.g., after electrical power to the CPU is switched from off to on, or "soft", where the power is not cut. On some systems, a soft boot may optionally clear RAM to zero. Hard and soft booting can be initiated by hardware such as a button press or a software command. Booting is complete when the operative runtime system, typically the operating system and some applications, is attained. Sequencing of Booting Booting is a start-up sequence that starts the operating system of a computer when it is turned on. A boot sequence is the initial set of operations that the computer performs when it is switched on. Every computer has a boot sequence. Types of Booting There are two types of booting in an operating system. Cold Booting: When the computer starts for the first time or is in a shut-down state and switch on the power button to start the system, this type of process to start the computer is called cold booting. During cold booting, the system will read all the instructions from the ROM (BIOS) and the Operating System will be automatically get loaded into the system. This booting takes more time than Hot or Warm Booting. 1. Warm Booting: Warm or Hot Booting process is when computer systems come to no response or hang state, and then the system is allowed to restart during on condition. It is also referred to as rebooting. There are many reasons for this state, and the only solution is to reboot the computer. Rebooting may be required when we install new software or hardware. The system requires a reboot to set software or hardware configuration changes, or sometimes systems may behave abnormally or may not respond properly. In such a case, the system has to be a force restart. Most commonly Ctrl+Alt+Del button is used to reboot the system. Else, in some systems, the external reset button may be available to reboot the system.